The Powerscreen Premiertrak 600 is an example of a material processing apparatus comprising a crusher, in particular a jaw crusher. The crusher is operated by rotating a fly wheel, rotational movement of the fly wheel being translated into reciprocating movement of a jaw within the crusher. The fly wheel may be driven by a direct drive system that is capable of rotating the fly wheel in one direction only. A problem with using the direct drive system is that it is cumbersome to remove material that becomes jammed in the crusher. In the event of a jam, the crusher must be emptied and the jammed material removed manually. The crusher must then be restarted while empty since the direct drive system is not suitable for starting under load conditions. As an alternative to the direct drive system, a hydrostatic drive system may be used that is capable of driving the fly wheel in either direction. This allows jams to be cleared automatically and without having to empty the crusher. However hydrostatic drives are relatively expensive and suffer from relatively poor fuel efficiency and power utilisation in comparison with the direct drive system.
It would be desirable to mitigate the problems outlined above.